1. Field of the Invention
The invention relates to a coating composition for the enteric coating of capsule halves made of water-soluble or water-swellable polymer material in the dipping process.
2. Description of the Related Art
Huyghebaert et al., European Journal of Pharmaceutical Sciences 21 (2004) 617-623, describe an alternative method for the enteric coating of capsules made of hydroxypropylmethylcellulose (HPMC) in which ready-to-use enteric capsule parts are obtained.
In the introductory section, it is reported that enteric coated HPMC capsules have for a long time been used in the dietetic food supplement industry as vegetarian alternatives to gelatine. It is also mentioned that although the enteric coating of hard gelatine capsules made of organic solutions is possible, it is difficult to execute and may lead to embrittlement of the capsules, which can result in poor adhesion of the coating. This can be overcome by applying an intermediate layer, although this is lengthy and complicated. Moreover, coating processes from aqueous preparations have the advantage over conventional coating processes in that gelatine capsules from organic solutions may be of concern on account of the toxicological and safety aspects. The coating of gelatine capsules from aqueous preparations, however, is very demanding and requires long processing times because of the solubility of the gelatine in water, which overall leads to high costs.
It is furthermore reported that, in contrast to gelatine capsules, HPMC capsules can be enteric coated relatively easily from aqueous preparations. However, it is necessary to additionally apply a sealing between the capsule halves, e.g. through a gelatine solution to be applied manually, in order to avoid an untightness of the capsule and an uncontrolled escape of the contents in the stomach. Another technique is to apply water/ethanol mixtures between the capsule halves and to weld the parts together at 40-60° C.
Using aqueous preparations (EUDRAGIT® FS 30 D, EUDRAGIT® L 30 D-55, Aquoat® AS-HF or Sureteric®) based on (meth)acrylate copolymers or polyvinyl acetate phthalate, plasticizers such as triethyl citrate and further auxiliaries, such as, for example, talc, it is possible to provide HPMC capsules with an enteric film. A separate sealing step can be dispensed with in the case of this coating technology. In particular, HPMC capsules which have been coated with (meth)acrylate copolymers are depicted as particularly advantageous am the sum of their properties.
It is furthermore mentioned that the dipping process for the enteric coating of capsules is very time-consuming and can bring with it a multitude of practical problems. In particular, the problems consist in an uneven coating and unsatisfactory enteric properties.
Problem and Solution
Capsules filled with active ingredients or food constituents, in particular made of gelatine or hydroxypropylmethylcellulose, have been used for a long time in the fields of pharmacy, food supplements and cosmetics. Active ingredients are to be understood as meaning in particular pharmaceutical active ingredients, food supplements or active ingredients with an assumed cosmetic effect, so-called cosmecuticals. Enteric coatings which are intended to prevent the capsule contents from being released in the stomach have likewise been known for a long time. Whereas capsule halves e.g. made of gelatine are produced with high precision in the dipping process, the enteric coatings for such capsules are produced almost exclusively in the spraying process. Attempts to apply enteric coatings in the dipping process have hitherto proven unsatisfactory.